1. Technical Field
The present invention relates to Wide Area Networks (WANs) and more particularly to a system and method for establishing Systems Network Architecture (SNA) sessions between SNA nodes through a packet/cell switching network using Telnet 3270 access services.
2. Description of the Related Art
Companies are increasingly interested in consolidating the multiple specialized networks that they operate or lease from service providers onto a single protocol network. These multiple specialized networks operate on diverse networking technologies such as SNA, Internet Protocol (IP) or Internetwork Packet Exchange (IPX). In making consolidation one of their top priorities, companies are almost exclusively selecting IP as their protocol of choice. For the overwhelming majority of these companies that are using SNA protocols and applications, however, there remains the need to maintain the ability to access the enormous quantity of existing corporate data that resides in traditional mainframes and only accessible through SNA applications.
In an IP environment, telnet technologies TN3270 and TN3270 Extended are widely utilized to transport SNA information across an IP network. This technique for SNA xe2x80x9cgreen screenxe2x80x9d workstation users employs a client/server approach. IBM""s xe2x80x9cHost On Demandxe2x80x9d or xe2x80x9cWebClientxe2x80x9d by CISCO are examples of client software implementations. Network Utility from IBM or CISCO router""s offerings are typical server implementations (hardware and software). The xe2x80x9cTN3270 clientxe2x80x9d component usually runs within the customer""s workstation while the xe2x80x9cTN3270 serverxe2x80x9d component is usually placed in front of the customer""s Data Center mainframes (or sometimes directly within the mainframe itself) or within the customer""s branch offices. As illustrated in FIG. 1, IP protocols (102) are used between a server (100) and clients (101), while traditional SNA protocols (103) are used between server (100) and target SNA applications (104) located within a mainframe.
More detailed explanations of telnet, TN3270, and Network Utility, can be found in the following publications incorporated herewith by reference: xe2x80x9cTCP/IP Tutorial and Technical Overviewxe2x80x9d by Martin W. Murhammer, Orcun Atakan, Stefan Bretz, Larry R. Pugh, Kazunari Suzuki, David H. Wood, International Technical Support Organization, October 1998, GG24-3376-05; xe2x80x9cInternet in a nutshellxe2x80x9d by Valerie Quercia, published by O""Reilly, October 1997; xe2x80x9cIBM 2216/Network Utility Host Channel Connectionxe2x80x9d, Erol Lengerli, Jacinta Carbonell, Thomas Grueter; IBM International Technical Support Organization, January 1999, SG24-5303-00; xe2x80x9cIBM Network Utility Description and Configuration Scenariosxe2x80x9d, Tim Kearby, Peter Gayek, Gallus Schlegel, Imre Szabo, Zhi-Yong Zhang; IBM International Technical Support Organization, January 1999, SG24-5289-00; xe2x80x9cInternetworking with TCP/IPxe2x80x94Volume Ixe2x80x94Principles, Protocols, and Architecturexe2x80x9d Douglas E.Comer, Second Edition, Prentice Hall 1991; Request For Comments (RFCs) from the Internet Engineering Task Force (IETF): RFC 1576: TN3270 Current Practices, RFC 1646: TN3270 Extensions for LU name and Printer Selection, RFC 1647: TN3270 Enhancements, and RFC 2355: TN3270 Enhancements.
Data transmission is evolving to focus on applications and to integrate a fundamental shift in the customer traffic profile. Driven by the growth of the number of intelligent (programmable) workstations, the pervasive use of local area network interconnections, the distributed processing capabilities between workstations and super computers, the new applications and the integration of various and often conflicting structuresxe2x80x94hierarchical versus peer to peer, wide versus local area networks, voice versus dataxe2x80x94the data traffic profile has become more bandwidth consuming, bursty, non-deterministic, and requires greater connectivity.
Based on the above observations, there is a growing need for supporting distributed computing applications across high speed wide area networks that can carry local area network communications, voice, video and data traffic among channel attached hosts, business or engineering workstations, terminals, and small to large file server systems. This vision of a high speed multi-protocol network has precipitated the emergence of fast packet switching network architectures such as the IBM""s Networking BroadBand Services (NBBS) architecture in which data, voice, and video information is digitally encoded, divided into small packets (of fixed or variable length), and transmitted through a common set of nodes and links. In this continuously evolving environment there remains the need for transporting xe2x80x9clegacyxe2x80x9d data traffic, such as SNA traffic across wide area networks.
To efficiently transport mixed traffic streams on very high speed lines requires a set of strict requirements in terms of performance and resource consumption that can be summarized as follows: a very high throughput and a very short packet processing time; an efficient set of flow and congestion control mechanisms; and a very large flexibility to support a wide range of connectivity options.
One of the key requirements of high speed packet switching networks is to reduce the end-to-end delays in order to satisfy real time delivery constraints and to achieve the necessary high nodal throughput for the transport of voice and video. Increases in link speeds have not been matched by proportional increases in the processing speeds of communication nodes. The fundamental challenge for high speed networks such as those based on NBBS technologies is thus to minimize the packet processing time and to take full advantage of the high speed/low error rate technologies.
Most of the transport and control functions provided by the new high bandwidth network architectures are performed on an end-to-end basis. The flow control and particularly the path selection and bandwidth management processes are managed by the access points of the network (where the NBBS access services reside), which reduces both the required awareness and functionality of the intermediate nodes.
Communication networks have at their disposal limited resources to ensure efficient packet transmissions. An efficient bandwidth management strategy is essential to take full advantage of a high speed network. While transmission costs per byte continue to drop year after year, these costs are likely to continue to represent the major expense of operating future telecommunication networks as the demand for bandwidth increases. Thus, considerable efforts have is been spent on designing flow and congestion control processes, bandwidth reservation mechanisms, routing algorithms to economically manage the network bandwidth.
An ideal network should be able to transmit an amount of traffic that is directly proportional to the traffic offered to the network to the maximum transmission capacity. Beyond this limit, the network should operate at its maximum capacity regardless of demand.
In high speed networks, the nodes must provide total connectivity. This includes attachment of end user devices, regardless of vendors or protocols. The network nodes must also be able to allow an end user device to communicate with any other device or group of devices, when justified or required. The network must support any type of traffic such as data (including xe2x80x9clegacyxe2x80x9d data), voice, video, fax, graphic or image related traffic. Nodes must be able to take advantage of all common carrier facilities and be adaptable to a plurality of protocols. All required conversions must be automatic and transparent to the end user.
The architectures of most high speed packet switching networks specify a set of generic services that offer end-to-end high bandwidth transport capabilities.
The present invention relates to transmissions in wide-area networks (WANs) based on the IBM""s NBBS architecture described in International Business Machine publication xe2x80x9cIBM International Technical Support Centersxe2x80x94Networking Broadband Services (NBBS)xe2x80x94Architecture Tutorialxe2x80x94GG24-4486-00xe2x80x9d dated June 95. NBBS services can be divided into three major areas
Transport Services:
Transport services provide a common infrastructure to support the transfer of information across the network. They are not used directly but through the access services (access Agents). Such transport services can be divided into three distinct functions: a Logical Link Layer; a Network Connection Layer; and the various Transport Protocols.
Network Control Services:
Network control services ensure that the transport and access services operate reliably, efficiently, and as automatically as possible. They are used to control, allocate, and manage the resources of the network on a real-time basis. They also provide network operators with the various facilities that are needed to configure, operate, and maintain the network on a day-to-day basis. This includes facilities for monitoring the performance of the network, accounting for its usage, and resolving problems.
Access Services:
Access services (access agents) provide an interface between the common high speed network (or backbone network) and external devices or networks via access link interfaces. The access services enable a wide range of external devices to get access to the common infrastructure provided by the transport services.
Together, the transport, network control and access services provide the capability to support communications between many different types of communicating devices through a common network infrastructure.
The TN3270 and TN3270 Enhanced (TN3270E) protocols require a full implementation of the complete suite of TCP/IP protocols. Implementing a full set of TCP/IP protocols is not only a complex task but also requires that each TN3270 node becomes a router with all the associated functionality. This results in complexities and severe overhead to account for router-to-router protocols that are not actually required for transporting SNA data. In traditional SNA networks, TN3270 services usually require a dedicated box, called a Telnet 3270 server. This Telnet 3270 server performs the conversion of SNA protocols to TCP/IP protocols and vice versa.
A method and system for establishing a Systems Network Architecture (SNA) session between SNA resources through a packet/cell switching network are disclosed herein. The packet/cell switching network includes an origin access node that provides client access services, and at least one destination access node that provides server access services. In accordance with the method of the present invention a SNA session request is received from a source SNA resource for establishing an SNA session with a target SNA resource. An undirected message is broadcast over the packet/cell switching network to identify the destination access nodes that support the source SNA resource and that provide server access services. One or more positive replies are received from respectively one or more of the destination access nodes that support the source SNA resource and that provide server access services. As part of the receiving step, information relating to a traffic handling capacity of the destination access node and information related to establishment of a connection between the origin access node and the destination access node is retrieved. Finally, a destination access node is selected in accordance with the information describing the destination node and in accordance with the information related to establishment of a connection between the origin access node and the destination node.
Establishing a connection between said origin access node and said selected destination access node in accordance with said selecting step.
All objects, features, and advantages of the present invention will become apparent in the following detailed written description.